Advancements in Robotic Lower Limb Prostheses: Development and Verification of Novel Technologies for Enhanced Mobility in Transfemoral Amputees

Every year, over a million individuals undergo lower limb amputations due to conditions such as diabetes, trauma, and vascular diseases. Among these, transfemoral amputations are particularly disruptive, modifying nat ural gait patterns, introducing compensatory movements, and increasing the metabolic demands of walking, ultimately compromising balance and overall quality of life. Robotic lower limb prostheses, which incorporate mo tors, sensors, and control algorithms, offer a promising solution by restoring joint function and improving mobility for transfemoral amputees. Although robotic prostheses are primarily confined to the research domain, the recent introduction of a few models to the market signals growing interest in these innovative solutions. As the field of robotic lower limb prostheses evolves, several challenges remain that must be addressed to ensure the widespread adoption of these devices and make user-prosthesis interactions seamless and intuitive. This thesis aims at advancing the design and control of robotic prostheses for individuals with transfemoral amputations through three main techno logical contributions. The first contribution is the advancement of the Sen sorized Prosthetic Foot (SPF), an optoelectronic sensory system designed to estimate biomechanical variables and detect gait events in real time. This work details the enhancements with respect to the first-generation design, including a robust single-PCB architecture with improved wiring integration and a streamlined assembly process. A calibration-free machine learning ap proach was developed to enhance force measurement accuracy and gait event detection. The second contribution involves the design and verification of the Syn ergy Prosthesis (SynPro), an underactuated knee-ankle prosthesis that lever ages natural kinematic synergies to coordinate multi-joint movements using a single actuator. Extensive bench testing and experimental verification with three transfemoral amputees demonstrated the compatibility of knee ankle underactuation for various locomotion tasks, including walking, stair negotiation, and sit-stand transitions. The third contribution is the development of a compact robotic knee prosthesis based on a series elastic actuator (SEA). This design incorporates a torsional SEA to achieve precise torque control and inherent compliance, facilitating a more natural interaction with the environment. A dynamic simulation framework was developed to aid components selection, allow ing to quickly assess various combinations of motors, transmissions, and spring stiffness. A continuously variable impedance controller was imple mented and compared with traditional finite-state machine control during level-ground walking and stair ascent. Results indicate that the variable impedance approach can deliver biomimetic performance and better align with clinically relevant goals with reduced tuning complexity, as demon strated in a case study with a transfemoral amputee. Overall, the innovations presented in this thesis represent significant ad vancements in prosthetic sensing technologies, design concepts that reduce power requirements, and enhanced user-prosthesis interaction. The promis ing results obtained so far have potential for future improvements, with the ultimate goal of transitioning advanced prosthetic technologies from the laboratory to clinical practice.